How to Convert an Object to a String in Python

# Table of Contents

1. Convert an Object to a String in Python
2. Convert a Class object to a String in Python
3. Converting a Class instance to a JSON string
4. Convert a Class object to a String using __repr__()

# Convert an Object to a String in Python

Use the str() class to convert an object to a string.

The str() class returns the string version of the given object.

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my_int = 42

# ✅ Convert an object to a string
result = str(my_int)
print(result)  # 👉️ '42'

print(type(result))  # 👉️ <class 'str'>
print(isinstance(result, str))  # 👉️ True

The first example uses the str() class to convert an object to a string.

The str() class takes an object and returns the string version of the object.

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my_obj = 3.14

result = str(my_obj)
print(result)  # 👉️ '3.14'
print(type(result)) # 👉️ <class 'str'>

If you need to convert a class object to a string, implement the __str__() method.

# Convert a Class object to a String in Python

Use the __str__() method to convert an object to a string.

The __str__() method is called by str(object) and the built-in format() and print() functions and returns the informal string representation of the object.

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class Employee():
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def __str__(self):
        return f'Name: {self.name}'


bobby = Employee('bobbyhadz', 100)

print(bobby)  # 👉️ Name: bobbyhadz

We defined the __str__() method on the class to convert it to a string.

The __str__ method is called by str(object) and the built-in format() and print() functions and returns the informal string representation of the object.

# Make sure to return a String from the __str__() method

Make sure to return a string from the __str__() method, otherwise a TypeError is raised.

For example, if we want to return the employee's salary from the __str__() method, we have to use the str() class to convert the value to a string.

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class Employee():
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def __str__(self):
        return str(self.salary)


bobby = Employee('bobbyhadz', 100)

print(bobby)  # 👉️ 100

The __str__() method is called if you use the object in a formatted string literal or with the str.format() method.

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class Employee():
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def __str__(self):
        return str(self.salary)


bobby = Employee('bobbyhadz', 100)

result = f'Current salary: {bobby}'
print(result) # 👉️ Current salary: 100

The __str__() method should return a string that is a human-readable representation of the object.

# Converting a Class instance to a JSON string

If you need to convert a class instance to a JSON string, use the __dict__ attribute on the instance.

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import json

class Employee():
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def __str__(self):
        return str(self.salary)


bobby = Employee('bobbyhadz', 100)

json_str = json.dumps(bobby.__dict__)
print(json_str) # 👉️ '{"name": "bobbyhadz", "salary": 100}'

We used the __dict__ attribute to get a dictionary of the object's attributes and values and converted the dictionary to JSON.

The json.dumps() method converts a Python object to a JSON formatted string.

# Convert a Class object to a String using __repr__()

There is also a __repr__() method that can be used in a similar way to the __str__() method.

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class Employee():
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def __repr__(self):
        return self.name


bobby = Employee('bobbyhadz', 100)
print(bobby)  # 👉️ 'bobbyhadz'

The __repr__ method is called by the repr() function and is usually used to get a string that can be used to rebuild the object using the eval() function.

# The difference between __str__() and __repr__()

A good way to illustrate the difference between __str__() and __repr__() is to use the datetime.now() method.

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import datetime

# 👇️ using __str__()
print(datetime.datetime.now())  # 👉️ 2022-09-08 14:29:05.719749

# 👇️ using __repr__()
# 👉️ datetime.datetime(2022, 9, 8, 14, 29, 5, 719769)
print(repr(datetime.datetime.now()))

result = eval('datetime.datetime(2023, 2, 21, 13, 51, 26, 827523)')
print(result)  # 👉️ 2023-02-21 13:51:26.827523

When we used the print() function, the __str__() method in the datetime class got called and returned a human-readable representation of the date and time.

We passed the string to the eval() function and created a datetime object with the same state.

Note that implementing the __repr__() method in this way is not always necessary or possible.

Having the __str__() method return a human-readable string is sufficient most of the time.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Convert a nested dictionary to an Object in Python
• Convert a string to a Class object in Python
• Convert a Map object to a List in Python
• Flake8: f-string is missing placeholders [Solved]